Structural characterization of MgO—Cr2O3—(Li2O) polycrystalline solids by e.s.r. methods

Abstract

The polycrystalline solids MgO—Cr₂O₃ and MgO—Cr₂O₃—Li₂O have been studied using e.s.r. methods. Three separate signals were obtained from the MgO—Cr₂O₃ specimens. These have been assigned to Cr³⁺ ions, first, in solid solution in sites of cubic symmetry, secondly, in a MgCr₂O₄ phase and thirdly, in solid solution in sites with axial symmetry. Two signals were obtained for the MgO—Cr₂O₃—Li₂O specimens. The first resonance has been attributed to Cr³⁺ ions in solid solution in MgO. The amount of this species increases on lithium addition up to [Li]/[Cr]= 1; above this ratio a new phase Li₂CrO₄ is formed. The second resonance is probably due to Cr⁵⁺ in the surface.